[资料][自动化技术][机器人]国外的机器人制作

RapidPrototypingofSmallRobotsDraftGrigoriyB.ReshkoCarnegieMellonUniversityPittsburgh,PA,[e-mail]rsityPittsburgh,PA,[e-mail]UniversityPittsburgh,PA,[e-mail]cribesourworkonhighqualityrapidprototyping.Thefocusisontechniquesthatproduceprototypesofdesiredqualityandyetdonottakelongtobuild.Wepresentnecessaryinformationaboutmethodsofcontrol,power,sensors,batteries,electronics,andmore.Weoutlinematerials,methods,andtools.Wealsoexplainhowtouseservomotors,Lego,andelectronicstoachievesatisfyingresults.Figure1showsanexampleofthekindofproject.Withtherighttoolsandmaterials,andwithpartsonhand,theomniwheeltelerobottooklessthanhalfanhourfromconceptiontocompletion.1.1Whyprototype?Wehavenoticedthatsomedesignerstendtoprototypeveryquickly[1].Sometimesyoucanlearnsomethingimportantinafewminutesfromaprototypethatmighthavetakenweeksormonthsotherwise.Mechanicaldesignseemstorequireiteration,so,thefasteryoucaniterate,especiallyatthebeginningofaproject,thebetter.1.2LevelsofprototypingPrototypingrangesfromanideatoacompleteproduct.Thequalityandthelevelofdetailofaprototypeshoulddependonitspurpose.Forexample,Figure1showsthefirstprototypeofthePalmPilotRobot[5],whichatthispointisnothingmorethanthreeservostapedtoareceiver.Thissimplemodelissufficienttofulfillitspurposeofdemonstratingholonomicmotionofthebase.Laterwebuiltamorecomplexprototypewithsensorstoshowthattherobotcanfollowwalls.2.ControlWeexaminedandtestedthreetypesofcontrolofprototypes:humanpoweredprototypes,remotecontrol,andcomputercontrol.2.1HumanpoweredprototypesOneofthemostcommongoalsofprototypingistodemonstrateaconceptoranidea.Usuallycomplexityofaprototypevarieswiththecomplexityofanidea.Relativelysimpleorpredictableprototypesdonotneedmotorsandbatteries–theycanbepoweredandcontrolledbyhumansinstead.Anexampleofahuman-poweredprototypeisaregularfour-wheelLEGOvehicleinFigure2.Thereisnoneedtoattachmotorsandremote-controlequipmenttodemonstratethatitcanmovebackandforth.Onthecontrary,itisimpossibletodemonstratewheeltractionsimplybyturningthewheels.Therefore,prototypesinwhichhumanFigure1Figure2RapidPrototypingofSmallRobots2interventionaffectstheresultsrequirearemoteorcomputercontrolsystem.2.2RemotecontrolHumanremotecontrolisusefulwhenpreciseorunusualmethodsofcontrolarerequired.Itisalsothesimplestwaytocontrolaprototypewithoutactuallyphysicallyinterferingwithit.Forexample,thefastestwaytodeterminewhathappenstoarobotthatrapidlyacceleratesandthendeceleratesistousearemotecontrolsystem.Asimpleandeasytouseremotecontrolsystemformodelairplaneswillsufficetodemonstratewhethersuchrobotwillimmediatelycometoastoporskidforacertaindistance.Suchcontrolsystemhasfourchannelsandprovidesgoodrange,reliablecommunication,anduptofourproportionalcontrols,whichallowsmoothadjustmentofspeedorangularpositionofservos.AnexampleisThree-WheelMobipulatorrobot.Humanremotecontrolprovidesaneasymethodofcontrolofthesteeredwheelandthebrakeatthesametime,whilenotrequiringanyprogrammingoradditionalelectronics.2.3ComputercontrolWhenarobotrequirespreciseandcomplexoperationsorisinvolvedinanapplicationthatrequiressensorsorcomputerfeedbacktotakeactions,thecomputercontrolbecomestherightchoice.Anexampleofsuchcontrolisasimpleautonomousprototypewithencodersonitswheelsdrivinginastraightpath.Companiesdevelopavarietyofboardswithdifferentcapabilitiesthatcancontrolservoandsteppermotorsbymeansofserialorparallelcommunicationwithacomputer.SomeboardsjusttranslatecommandsfromacomputertoPWMsignals,whereasothersareprogrammable.Pontech’sSV203boardisagoodexampleofarelativelysimpleandinexpensivecomputercontrolsystem.Itusesserialcommunicationtotalktoacomputerandcanrunbyitself.However,itisveryslowandsimplisticcomparedtoadesktopcomputer.Mostboardshaveverylimitednumberoffunctionsandtheamountofmemory.Althoughtheboardbyitselfcanbesufficientforanumberofapplications,thetwoalternativesaretouseatetherandconnectarobottoareasonablypowerfulcomputer,ortouseamorecomplexboardsuchas68HC11chiporBASICstamp.Anotheradvantageofcomputercontrolovertheprevioustwomethodsistheabilitytousesensors.Mostcontrolboardshavealreadybuilt-inanaloganddigitalinputsandcanconnecttoavarietyofsensors.3.PowerSize,shape,andvoltageofbatteriesdependonitsapplication.Forsmall-scaleprototypes,weuse6Vor4.5VNickel-MetalHydride(NiMH)battery.Itisfullyrechargeableandcanprovidesteadyvoltageforarelativelylongtime.Thesebatteriescanbeusedforservomotorsandelectronics,becausetheyprovidehighcurrent.Asmallregular9Vor6VNiMHwithavoltageregulatorcanbeusedtopowerelectronics,sinceitdoesnotrequirehighcurrent.Tetheredmodelscanbepoweredexternally,sincetheyalreadyrequirewiresforcommunication.Externalpowersupplyhasanadvantageofprovidingstablehigh-currentoutputwithoutaneedtorecharge.4.SensorsWhencontrollingarobotbyacomputer,orwhenitisanautonomoussystem,sensorsbecomeanintegralpartofprototyping.4.1.DigitalandanalogsensorsTherearetwotypesofsensors:digitalandanalog.Digitalsensors,suchasmicro-switchesorpushbuttons